"Giants Mollusks are released from the earth by an earthquake and start killing people."
Tim Holt
as Lt. Cmdr. John 'Twill' Twillinger
Audrey Dalton
as Gail MacKenzie
Hans Conried
as Dr. Jess Rogers
Barbara Darrow
as Jody Simms
Max Showalter
as Dr. Tad Johns
Harlan Warde
as Lt. Robert 'Clem' Clemens
Gordon Jones
as Sheriff Josh Peters
Mimi Gibson
as Sandy MacKenzie
Marjorie Stapp
as Connie Blake
Jody McCrea
as Seaman Fred Johnson
Wallace Earl
as Sally
Dennis McCarthy
as George Blake (lab assistant)
Sarah Selby
as Mrs. Simms
Milton Parsons
as Lewis Clark Dobbs
Charles Tannen
as Seaman Wyatt (Radioman)
Robert Benevides
as Seaman Morty Beatty
John Carlyle
as Monster Victim
John Close
as Deputy Larry
William Forrest
as Admiral Greenhouse
Gil Frye
as Deputy Scotty
Joseph Hamilton
as Other Lock Watchman
Charles Herbert
as Boy with Morty's Cap
Byron Kane
as Coroner Nate Brown
Ralph Littlefield
as Gatekeeper
David McMahon
as Patterson
Ralph Moody
as Watchman at Lock 57
William Swan
as Seaman Howard Sanders
Hal Taggart
as Davis - Resort Owner
Mack Williams
as Captain Masters
Dan Gachman
as Deputy Brewer
Michael Dugan
as Clarke
David Duncan
Story
Arnold Laven
Director
Heinz Roemheld
Conductor
Virginia Mazzuca
Production Assistant
Joel Moss
Sound Recordist
Charles Althouse
Arthur Gardner
Producer
Pat Fielder
Screenplay
Kerwin Coughlin
Casting
Augie Lohman
Special Effects
Lester White
Director of Photography
James Dowell Vance
Art Direction
Jules V. Levy
John Faure
Editor
Original Music Composer
Rudy Butler
Set Decoration
Paul Stader
Other
Olga Collings
Hairstylist
Ted Haworth
Allen Sloane
Wardrobe Supervisor
Norman Bishop
Technical Supervisor
Robert H. Crandall
Scotty Welbourne
Underwater Director of Photography
Abe Haberman
Makeup Artist
Music Director
Sound Mixer
Maurice Vaccarino
Assistant Director
Paul Eagler
B. F. Remmington
